1. Field of the Invention
The present invention relates to a relay station, a transmission method, and a tangible machine-readable medium thereof for use in a multi-hop network. More specifically, the present invention relates to a relay station, a transmission method, and a tangible machine-readable medium thereof for use in a multi-hop network based on the IEEE 802.16j standard.
2. Descriptions of the Related Art
The IEEE 802.16j standard provides two kinds of relay modes: transparent relay and non-transparent relay modes. A relay station (RS) conforming to the IEEE 802.16j standard works in one mode at a time. FIG. 1A illustrates a multi-hop relay system 1 conforming to the IEEE 802.16j standard, wherein the multi-hop relay system 1 comprises a multi-hop relay base station (MR-BS) 11, a relay station (RS) 13, and a mobile station (MS) 15. The multi-hop relay system 1 operates in the transparent mode, that is, the MS 15 associated to the RS 13 is located within the coverage 12 of the MR-BS 11.
FIG. 1B illustrates a frame structure of the IEEE 802.16j standard. When the MR-BS 11 intends to transmit data to the MS 15, it has to allocate resources in the downlink (DL) MAP in a frame. After that, the MR-BS 11 transmits the data to the MS 15 in a burst of this or the next frame according to the DL MAP. On the other hand, the MR-BS 11 can allocate resources in the uplink (UL) MAP in a frame as well. Then, the MS 15 can transmit to the MR-BS 11 in a burst of this or the next frame according to the UL MAP.
In the transparent mode, the MR-BS 11 transmits data and a control signal through different paths to the MS 15. To be more specific, the control signal, i.e. both the DL MAP and UL MAP is directly transmitted from the MR-BS 11 to the MS 15 without the relay of the RS 13, while the data is transmitted from the MR-BS 11 to the MS 15 with the relay of the RS 13. All the MS 15 and the RS 13 within the coverage 12 are synchronized to the MR-BS 11 according to the preamble in a frame issued by the MR-BS 11 and then get the DL MAP and UL MAP.
However, some problems will occur when a new RS intends to join the multi-hop relay system 1. First, the new RS has to support the aforementioned UL/DL data relay. Second, since the joining of the new RS provides additional paths to the existing MS, the MR-BS 11 and the new RS have to support routing path management. Third, broadcast and multicast of DL data have to be achieved in a more efficient way. Consequently, a solution to the problems is still an objective for the industry to endeavor.